Scanning head structure for wide band magnetic record/reproducing tape and method of its manufacture

Abstract

To provide for accurate relocation of two cylindrical halves of a scanning head after diassembly, for example for replacement of scanning transducers, a cylindrical element is located adjacent a support block having a surface approximately matching the surface of the cylindrical scanning head and additionally includes bearing seats formed of cast, or molded material in engagement with the cylindrical portions in positioning the portions on the support block; the cast or molded projection may, for example, be made of cured epoxy, cast through holes in the support block and prevented from adhesion with the cylindrical parts by a separating element.

I claim: 
     
       1. Scanning head structure for wide band magnetic recording/reproducing tape (11), particularly for video tape recording having a stationary cylindrical guide drum (10) formed with two cylindrical portions (12, 13) axially separated by a gap and means (14, 15) guiding the tape about a portion of the circumference of said drum in a spiral path, said drum being adapted to have a transducer head wheel rotatable therein in a plane transverse to the axis of the cylindrical drum to scan an inclined path across the tape as the tape moves over the drum; and   a block-like support structure (16) separable from said drum located adjacent a portion of the surface of the drum extending axially alongside the drum and positioning the portions (12, 13) of the drum with respect to each other and having a surface facing the drum which approximately matches the drum surface, said structure being formed with openings extending therethrough and terminating at the surface thereof facing the guide drum (10);   and bearing seats (17, 18, 19, 20; 21, 22, 23, 24) comprising a hardened cast, or molded material located in said openings, projecting from the surface of the block-like structure facing the drum and in engagement with the portions (12, 13) of the drum and accurately positioning said portions on and with respect to the block-like structure (16).   
     
     
       2. Structure according to claim 1 further comprising bearing blocks (40, 41) attached to said block-like structure (16) to provide bearings for the tape guide means (14, 15); and bearing sleeves (42, 43) comprising cast, or molded material in said bearing blocks.   
     
     
       3. Structure according to claim 1 wherein the cast, or molded material comprises a hardened, or cured resin. 
     
     
       4. Structure according to claim 3 wherein the hardened, or cured resin is an epoxy resin. 
     
     
       5. Structure according to claim 4 wherein the epoxy resin is curable, upon addition of a curing agent, at room temperature. 
     
     
       6. Structure according to claim 3 wherein the resin includes a filler material. 
     
     
       7. Structure according to claim 6 wherein the filler material includes milled quartz. 
     
     
       8. Structure according to claim 7 wherein the proportion of milled quartz to resin is, by weight, approximately 26% resin and 74% milled quartz. 
     
     
       9. Structure according to claim 1 wherein said block-like structure is made of a lightweight metal. 
     
     
       10. Structure according to claim 1 wherein said bearing seats are formed as button-like projections extending at discrete positions slightly outside of said surface on the block-like structure facing the drum. 
     
     
       11. Structure according to claim 1, wherein said block-like structure (16) is made of light-weight metal and the cast or molded material comprises a hardened, or cured resin which is dimensionally stable upon setting or curing and is essentially immune with respect to shrinking or expansion upon curing. 
     
     
       12. Structure according to claim 11, wherein the resin includes a filler material. 
     
     
       13. Method of making a scanning head structure for wide band magnetic recording/reproducing tape (11), particularly for video tape recording, having an essentially cylindrical drum (10) and a block-like support structure (16) on which the drum is to be secured in accurately positioned relation, the structure having a surface facing the essentially cylindrical drum and approximately matching the cylindrical surface of the drum,   comprising the steps of   forming a plurality of openings (17'-24') extending through said block-like structure and terminating at said surface;   fitting a fill foil against said surface, while leaving said openings uncovered;   providing a mandrel (1) having a cylindrical structure similar to the drum (10);   coating the mandrel (1) with a separating medium;   introducing a flowable hardenable casting, or molding compound through said openings from a region of said block-like structure remote from said surface until said casting, or molding compound contacts the mandrel;   and permitting said casting or molding compound to harden to form a seating, or bearing area (17, 18, 19, 20; 21, 22, 23, 24) for the drum which is unvarying with respect to the support structure.   
     
     
       14. Method according to claim 13 wherein the step of introducing said casting or molding compound is carried out under essentially pressure-less conditions. 
     
     
       15. Method according to claim 13 wherein the block further includes bearing means (40, 41) for tape guide rollers; and further including the step of introducing the bearing sleeve liner compound into said bearing blocks to form a bearing sleeve liner (42, 43).   
     
     
       16. Method according to claim 13 wherein said block-like structure (16) includes locating bores (17, 25) and guide slits (26); further including the step of introducing core, material into said locating bores and guide slits.   
     
     
       17. Method according to claim 13 wherein said casting or molding material comprises a hardenable, or curable resin. 
     
     
       18. Method according to claim 17 wherein said resin comprises an epoxy resin and a curing or setting agent, curing at room temperature. 
     
     
       19. Method according to claim 17 wherein said resin is dimensionally stable upon setting or curing and is essentially immune with respect to shrinking or expansion upon curing. 
     
     
       20. Method according to claim 17 further including a filler material in said resin. 
     
     
       21. Method according to claim 20 wherein said filler material comprises milled quartz. 
     
     
       22. Method according to claim 21 wherein the proportion of filler material to resin, by weight, is approximately 26% resin and 74% filler material. 
     
     
       23. Method according to claim 13, wherein said block-like structure (16) is made of light-weight metal and the cast or molded material comprises a hardened, or cured resin which is dimensionally stable upon setting or curing and is essentially immune with respect to shrinking or expansion upon curing. 
     
     
       24. Method according to claim 23, further including a filler material in said resin.